1. Field of Invention
The field of the invention relates to a landing zone (LZ) kit used to provide a temporary landing zone for helicopters. In order for this kit to do its job properly it must indicate to the pilot the location of the landing zone during both daytime and nighttime conditions. In addition, during the landing process the helicopter generates substantial wind. Therefore the deployed components of the landing zone kit must resist being displaced from their proper locations by the rotor wash of the helicopter. In order to minimize displacement it is important that the components resist rolling on the ground or becoming airborne and striking the helicopters blades.
During nighttime landings pilots often employ night vision goggles to aid them during the landing process. Therefore the landing zone kit must be designed to avoid overwhelming or blinding the night vision goggles being employed. The landing zone kit will overwhelm night vision goggles if the landing zone lights emit excessive amounts of visible, infrared, or infrared combined with visible radiation towards pilots flying with night vision goggles. Excessive amounts of visible light directed towards pilots flying with the unaided eye can also blind the pilot thereby creating a serious hazard. Landing zone kits that employ incandescent or xenon strobe lamps can present problems for the pilot as these traditional light sources commonly simultaneously emit large amounts of infrared light whenever they are emitting visible light. This combination of emitted energy can easily overwhelm night vision goggles.
The landing zone kit must include lights which are bright enough to be visible from a substantial distance so the pilot can locate the landing zone. However, as the aircraft approaches the landing zone the lights must reduce the intensity directed towards the pilot so that they will not blind the pilot's unaided eye or overwhelm his night vision goggles. This potential problem can be avoided by adding an optic or lens to each light to concentrate the light about the horizontal thereby creating a light beam directed about or slightly above the horizontal. The typical light beam has an angular beamwidth of approximately ten degrees which is intense enough to be visible by the pilot from a substantial distance as he approaches the landing zone. However, as the helicopter becomes close to the landing zone the pilot's line of sight is angled well above the horizontal and therefore out of the high intensity beamwidth created by the lens. At this angular position—out of the concentrated light beam—the intensity of the light impinging upon the pilot is substantially reduced permitting the pilot to complete the landing without excessive intensity.
It is common for helicopters to have powerful flood lights. It is therefore desirable to use the helicopter flood lights as an aid to assist the pilot to precisely locate the landing zone as the helicopter hovers over it.
It is difficult for the battery-powered lights of a typical landing zone kit to be powerful enough to provide adequate visibility during daytime landing operations. Therefore it is problematic for commercially offered kits to function adequately during daytime or during bright sunlight landings.
Commercial landing zone kits do not provide a reflectorized weighted base backup system which assures the pilot an adequately identified landing zone in the event that one or more of the lights in the kit fail.
Commercial landing zone kits must be lightweight and compact as they are frequently stored in small compartments on emergency vehicles. It is problematic to create a portable landing zone kit that is compact and lightweight yet which solves the problems related to landing zone identification including: tall grass obstruction, lights that are visible at great distances, daytime visibility and stability against rotor wash.
2. Prior Art
It is common for medical evacuation helicopters to be required to land at accident scenes so that they can transport injured people to proper medical facilities. First responders are tasked with the responsibility of locating and identifying a proper landing zone for these helicopters. It is critical that the pilot of an arriving helicopter have the landing zone marked such that he can easily and quickly locate both the perimeter of the landing zone and the wind direction within the landing zone.
Prior art includes a variety of landing zone kits for the problem of setting up temporary landing zones for helicopters. A first prior art kit solution (see web page www.etipinc.com) employs five xenon strobe lights. Four of the strobe lights (perimeter lights) are placed at the corners of the landing zone in a square pattern to indicate the proper landing location for the helicopter. The fifth strobe light is placed midway between two perimeter lights to indicate the wind direction for the helicopter pilot. This method of delineating the landing zone is commonly known. The xenon strobe lights are constantly flashing. This flashing of five lights can be confusing to the pilot. Furthermore the duration of the flash of a xenon strobe is extremely short making it difficult from a depth perception perspective to accurately locate the corners of the landing zone. Five flashing lights each having an extremely short flash duration can confuse a pilot or at the very least make it difficult for the pilot to precisely and quickly locate the landing zone. This first prior art kit often also includes several sets of five lenses each. Each set of lenses is of a different color permitting the user to change the color of the entire five lights as desired. For example, it is common for this kit to include five red lenses, five amber lenses and five white lenses. Since the xenon strobe light produces a broad spectrum of emitted light each color lens permits that color of light to pass. Sometimes a group of infrared lenses is also included. The strobe lights emit both visible and infrared energy. The infrared lenses block the visible light transmitting only the infrared light which is visible only to pilots using night vision goggles. The lights in this first prior art kit have a magnet at their underside which attaches to a steel weight or base to provide stability of the assembly during rotor wash. The steel weights are small in size having a surface area of approximately 16 in2. In addition, the weights are not painted with a bold or fluorescent color and when deployed they are substantially covered by the lights. The small projected area of these weights—when viewed from above—does not provide useful visibility during daytime operations. The individual lights are powered by two AA batteries each with their axis parallel to the horizontal. This battery disposition creates a low profile for the lights which is approximately 1.5 inches tall. This design offers little wind resistance because of its low profile and small size. This reduces the possibility of their being shifted by rotor wash winds and it makes the landing zone kit beneficially compact. Unfortunately the low profile of the lights substantially reduces their visibility if they are surrounded by tall grass.
This first prior art kit creates a number of difficulties for pilots. The xenon strobe lights emit light covering a wide range of wavelengths including infrared. This causes a problem for pilots flying with night vision goggles which respond to both visible and infrared light. The goggles can be blinded (overwhelmed) by the combined energy of the multi-wavelength light emitted from the strobe light. In addition the strobe lights only flash. The flashing of five lights within the landing zone can both blind and confuse the pilot. It is noteworthy that the supplier of this kit supplies five lenses of each color and does not suggest mixing colors. Since this first kit illuminates all five lights with a single color it opens the door to pilot error as the pilot may confuse the wind direction light with the perimeter lights.
A second prior art kit (see webpage www.aircraftspruce.com) is similar to the first prior art kit except in addition to the five flashing beam light modules it optionally includes five steady beam light modules. This option permits the user to change all of the xenon strobe landing zone lights into steady beam incandescent lights by changing the light modules. This steady light beam option eliminates the problem of several flashing lights confusing the pilot. However it still does not permit the pilot to distinguish between the perimeter lights and the wind direction light. In addition if the five steady beam light modules are employed the pilot can fail to locate the landing zone which now can be confused with other steady lights in the area. This second prior art kit employs two C cell batteries axially aligned along a vertical. The included light is 9.5 inches tall and is permanently attached to a round base which is 6 inches in diameter. The light and the base are orange in color and the combination weighs 3.5 pounds. The 6 inch diameter base has a circular periphery and a projected area of approximately thirty square inches when viewed from directly above by a helicopter pilot. Pilots searching for a landing zone must locate it from a distance and the projected area of the base is substantially reduced as the helicopter approaches the landing zone and the angle of viewing changes. An approaching pilot may view the base at a substantial angle of divergence from the vertical making the base appear substantially smaller than it actually is. A base having thirty square inches is too small of a target for a pilot searching for a landing zone. Since the lights and bases are permanently connected there is no way to deploy the bases separately for daytime landings. The bases are not large enough to provide reasonable visibility to an approaching pilot and not coated with fluorescent paint which would be employed if bright sunlight visibility were an objective. There is no indication that the weighted bases were intended for daytime visibility. In this design the light is permanently attached to the base. Therefore if rotor wash pushes the light horizontally the base will be rotated upward and can be caught by the wind. This is undesirable as the base/light assembly can be displaced. Due to its round perimeter the base can roll to an undesirable location.
The light is tall and therefore beneficially emits its beam of light above tall grass. It employs C cell batteries which have a large diameter relative to AA cells. The large diameter C cells result in a light having a large body diameter and therefore a large horizontally projected area. This design is not a desirable result as it increases the wind resistance and positions the center of gravity of the design substantially above ground level decreasing the stability of the assembly. The large horizontally projected area and tall light combine to encourage the rotor wash winds to develop forces and torques adequate to displace or overturn the light assembly. Additional weight can be added to correct the stability problem but additional weight is not desirable when transporting the LZ kit.
A third prior art kit (see www.rescuetech1.com) provides five lights each of which incorporate LED bulbs. Each light can—by rotating a bezel—emit either a flashing or steady beam. The housings of the lights are fluorescent yellow and can include reflective tape on their body. The lights are held upright by means of a black rubber base. Lens colors are offered in sets of four orange and one blue or four amber and one blue. This third prior art kit uses the color of the emitted light to differentiate between the four perimeter lights and the wind direction light. It also employs LED lamps. Lights that employ LED lamps normally require that the LED lamps be changed in order to change the color of the emitted light because LED lamps emit light only within a very narrow nanometer (nm) bandwidth, LED lamps normally do not emit significant amounts of infrared light if they are emitting visible light. Hence it is usually inefficient and sometimes impossible to change the color of the emitted light from an LED light source by changing a lens or filter. Therefore, in this prior art design the color of emitted light is mostly determined by the LED lamp chosen for the product. Color lenses are employed only for very minor adjustments in color or as indicators of the color of the light which will be emitted by the LED lamps.
This design does beneficially permit pilots flying with the unaided eye to locate both the perimeter of the landing zone and the wind direction. However pilots flying with some night vision goggles can have a serious problem as some goggles attenuate light at the wavelengths represented by blue LED lights. Pilots using some filtered night vision goggles will have trouble seeing the blue LED wind direction lights as the blue wavelengths are blocked and the LED lamps emit very little infrared light. This is problematic as knowing wind direction is critical to a safe landing and takeoff.
A fourth prior art landing zone design used by the military can be found on website www.ehow.com/how_8526360_set-military-landing-zone-kit.html. The military employs fabric landing zone markers which are approximately 3′×3′. The fabric is coated with a fluorescent orange coating. In addition it is coated with a reflective coating. The fabric is secured to the ground by placing locally obtained rocks around its periphery. The military landing zone kit also employs glow sticks known as Chemlights™ in place of the battery-powered lights used in commercial kits. Glow sticks are chemically activated lights which—once activated—emit light in all directions. The emitted light is a steady beam of a narrow bandwidth similar to an LED light source. It is not very intense as the light is not concentrated by a lens. The military is known to have its own requirements, so what works for them, may not be acceptable for civilian pilots.
For example, civilians may not have available rocks to prevent the fabric from being blown away. Also the lights are not bright enough for the civilian world in which the lights marking the landing zone have to compete with nearby civilian lighting. Finally, although the fabric is coated with fluorescent orange and reflective paints it does not stand out or provide the visibility of a smooth, flat fluorescent orange or reflective surface because the wrinkled fabric reduces the visibility of both the fluorescent orange and reflective paints. In order to avoid being easily displaced by rotor wash the fabric markers are of a heavy material. Therefore a group of these markers—as would be required in a landing zone kit—would be unacceptably bulky when considered for civilian use.
3. Objects and Advantages
The objects and advantages of the present invention are to provide a landing zone kit that achieves the following:                It is—when deployed—visible both to pilots with class A night vision goggles and pilots flying with the unaided eye (without night vision goggles), yet it does not overwhelm the night vision goggles with excessive energy as it provides visible light sufficient to be seen with the unaided eye.        It includes weighted bases having sufficient surface area and coloring to make them visible to pilots attempting to locate the landing zone in bright sunlight, thereby permitting the landing zone to be identified during daytime without lights.        It includes weighted bases that are heavy enough to prevent displacement during rotor wash even considering that these bases have a projected surface area large enough to ensure daytime disability.        It includes lights and weighted bases which can be used separately or as an assembly.        It includes AA batteries axially aligned along a vertical permitting a light housing having a nominal diameter which is minimized, therefore minimizing the forces applied to the light assembly due to rotor wash winds. Minimizing the forces due to rotor wash makes the light assembly more stable permitting a design of reduced weight.        It includes three AA batteries having minimal weight axially aligned along the vertical in place of the relatively heavy C and D cells used by prior art. The light component of the present invention can therefore be substantially lighter in weight then prior art designs having their batteries axially aligned along the vertical Consequently, for a light/base assembly of limited weight the base of the present invention can weigh more than the base component of prior art. Having the light component of less weight than the light component of prior art and a base component of greater weight than the base component of prior art results in the more stable (wind resistant) lighting assembly of the current invention.        It employs AA batteries, which unlike C or D cell batteries are readily available as alkaline, rechargeable or lithium batteries. By employing AA batteries the present design permits the choice of AA lithium batteries which are substantially lighter in weight than the alkaline or rechargeable batteries. The reduced weight option is especially important for designs which axially position the batteries because axially positioned designs tend to have their center of gravity high making them unstable. Designs employing C and D cell batteries cannot lower their center of gravity by switching to readily available lithium batteries.        It includes lights that have emerging light beams of the wavelengths and beam patterns necessary to avoid overwhelming class A night vision goggles when pilots are landing with night vision goggles yet which assure nighttime and dusk visibility for those pilots landing with the unaided eye.        It includes weighted bases that have a reflectorized smooth surface projected surface area that will efficiently reflect the light from the helicopters floodlight back to the pilot, thereby aiding the pilot in precisely locating the landing zone. In addition the bases act as a failsafe identifier of the landing zone in the event of landing zone light failure. The smooth surface of the reflectorized area makes the reflecting process more efficient, and therefore permits a reduction in the size of the base and the reflective zone over the prior art reflective fabric. Reducing the size of the weighted base is beneficial as it makes the entire kit more compact and lighter in weight.        It includes weighted bases and landing zone lights, both of which are color-coded and color coordinated to distinctly identify both the perimeter and the wind direction. It further coordinates the perimeter lights with the perimeter weighted bases by coloring them with a first color group. Similarly it coordinates the wind direction light with the wind direction weighted base by coloring them with a second color group. This design feature permits pilots to identify both the wind direction and the perimeter during daylight, dusk and evening.        The present invention permits pilots flying with night vision goggles to identify and separate wind direction and perimeter lighting. Pilots flying with night vision goggles cannot differentiate between colors. Therefore, using colors to separate wind direction from perimeter lights will not function for pilots flying with night vision goggles. The present invention uses different light modes to separate wind direction from perimeter lighting. Typically, the wind direction light is pulsing or flashing and the perimeter lights are steady. Therefore, even when flying with night vision goggles and even though the pilot cannot differentiate colors he can identify the wind direction as the pulsing light. The preferred embodiment of this invention employs four steady mode perimeter lights and one flashing mode wind direction light. Although the modes could be switched between perimeter and wind direction lighting the preferred embodiment is selected so that the pilot will not be confused by a plurality of pulsing lights. Prior art has offered five landing zone lights permitting the user the option of making all of the lights either steady or flashing. This is done because even though five flashing lights can be distracting and confusing some pilots prefer flashing lights in city areas to differentiate the landing zone from steady beam surrounding lighting. Other pilots especially in rural areas prefer five lights emitting steady light which is not distracting. In having a single light flashing the present invention offers a landing zone kit which is identifiable in both in rural and city areas and which also separates wind direction from perimeter lighting for pilots with night vision goggles.        It includes rectangular weighted bases and a rectangular carrying case which cooperate to reduce the space required to store the landing zone kit. First responders such as fire and police are required to carry a substantial amount of equipment in their vehicles. Space is valuable and a landing zone kit which is too bulky or heavy will not be acceptable. Rectangular weighted bases fit compactly in rectangular carrying cases effectively reducing the storage space required for the LZ kit,        
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